Immunoassays and nucleic acid hybridization chemistries are rapidly being developed towards the goal of detecting genetic defects, performing disease diagnostics, and performing prognostic evaluations (Sosnowski et al. (1997) Proc. Natl. Acad. Sci. USA, 94: 1119-1123). Antibodies, nucleic acid binding proteins, receptor ligands, and nucleic acids are known to bind very specifically and with high efficiency to their congnate "binding partner" under suitable conditions. This phenomenon is frequently used for the recognition and diagnosis of disease-causing organisms (e.g., HIV), pathological conditions (e.g. cancer, liver disease, kidney disease, degenerative joint disease, etc.), substance abuse (e.g. detection of products such as cotinine, etc.), and the like.
Numerous disease markers, and pathogen markers (e.g. proteins and/or nucleic acids) are well known and have been thoroughly characterized. Thus, binding partners (e.g. nucleic acids, antibodies, and the like), that specifically bind such markers can be synthesized and/or isolated and used as markers for recognition of the disease state, or disease-causing agent (Landegren et al. (1988) Science, 242: 229, Mikkelson (1996) Electroanalysis, 8: 15-19). Various assays are carried out routinely in microbiology laboratories or pathology laboratories using such methodologies.
Nucleic acid hybridization, antibody binding reactions, protein binding reactions, and lectin binding reactions are generally detected through the use of labels that either intercalate into the molecule (e.g. into the double helix of a DNA) or are covalently attached to either the target or the probe molecule (see, e.g., Sosnowski et al. (1997) Proc. Natl. Acad. Sci. USA, 94: 1119-1123, LePecq and Paoletti (1966) Anal. Biochem., 17: 100-107, Kapuscinski and Skoczylas (1977) Anal. Biochem., 83: 252-257). In some cases, electrogenerated chemiluminescence has also been utilized to detect an intercalated electroactive luminescent marker (Pollard-Knight et al. (1990) Anal. Biochem., 185: 84-89, Pollard-Knight et al.(1990) Anal. Biochem., 185: 353-358, Tizard et al. (1990) Proc. Natl. Acad. Sci. USA, 12: 4514-4518). All of these detection strategies require the derivatization of the target or probe molecule, either before (e.g. for covalent labeling) or after (e.g. for intercalation or indirect labeling) the binding reaction between the probe and target molecule. This introduces contamination problems. In addition, where multiple analytes are analyzed simultaneously multiple labels must be employed. In addition, tedious sample handling is required which further enhances the risk of contamination and/or leads to false analysis. These and other problems are overcome by the present invention.